As a related art of the present invention, Japanese Patent No. 4493686, for example, discloses a porous capacitor in which a plurality of substantially columnar holes are formed in a dielectric layer provided between a pair of conductor layers opposed to each other at a predetermined interval, an electrode material is filled in these holes to form first electrodes and second electrodes, the first electrodes are electrically connected only to one of the conductor layers, and the second electrode is electrically connected only to the other conductor layer.
FIG. 11 is a structural diagram of the porous capacitor of the related art. In this figure, a porous capacitor 1 is configured as follows: a dielectric layer 4 is interposed between a pair of conductor layers (hereinafter referred to as the first conductor layer 2 and the second conductor layer 3) opposed to each other at a predetermined distance; a large number of holes 5 orthogonal to the first conductor layer 2 and the second conductor layer 3 and having a substantially straight tubular shape are formed in the dielectric layer 4; an electrode material is filled in these holes 5 to form first electrodes 6 and second electrodes 7; the first electrodes 6 are electrically connected only to one of the conductor layers (the first conductor layer 2); and the second electrodes 7 are electrically connected only to the other conductor layer (the second conductor layer 3).
The porous capacitor 1 of the related art has a large number of electrodes (the first electrodes 6 and the second electrodes 7) formed in the porous dielectric layer 4, the electrodes being connected selectively to the first conductor layer 2 and the second conductor layer 3. This arrangement increases the area of the electrode plate and thus increases the capacitance without increasing the size of the capacitor.